Ligands and Coordination Numbers (Problem 6D.15) [ENDORSED]

[Rhea McKenzie 2J]

How are we supposed to know that Al3+ is surrounded by 6 water molecules (i.e., has a coordination number of 6) in order to form the reaction equation for part b of problem 6D.15?

6D.15
Calculate the pH of (b) 0.055M AlCl3

This is the reaction equation I found online after multiple attempts of creating one myself:

Do we have to know about ligands and coordination numbers in preparation for Midterm 1? If not, is there a way to solve/approach this problem without utilizing such information?

[Chem_Mod]

This detail will not be expected.

Ligands and coordination numbers are Chem 14A material, and not tested in Chem 14B.